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Questions This online section, designed for additional skill mastery, includes 50 ECG cases, grouped thematically. They are of varying levels of difficulty, ranging from entry level to much more challenging. Good luck! This part is self-scored. Working in small groups may be helpful. Life-Savers: Stat ECG Diagnoses The following five patients all have different life-threatening problems that you can diagnose from their electrocardiograms ECGs without any…

General Readers interested in understanding more about the underpinnings of electrocardiogram (ECG) interpretation should refer to the series of six scientific statements included in the Recommendations for the Standardization and Interpretation of the Electrocardiogram . These landmark articles, written under the auspices of the major cardiology societies, are highly recommended to students and experts alike. The full texts are freely available at societies’ websites, including via…

Part I: Basic Principles and Patterns Chapter 1: Essential Concepts: What is an ECG? Review An electrocardiogram ( ECG or EKG ) is a graphical (voltage as a function of time) recording of some of the electrical activity generated by heart muscle cells. The electrical signals are detected by means of metal electrodes . For a standard 12-lead ECG the electrodes are placed on the patient’s…

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We have focused most of our attention on the major clinical uses of the electrocardiogram (ECG). This review and overview chapter (1) underscores some important limitations of the ECG, (2) reemphasizes its utility, and (3) discusses some common pitfalls to help clinicians avoid preventable errors. Important Limitations of the ECG The diagnostic accuracy of any test is determined by the percentages of false-positive and false-negative results…

ECG Reading: General Principles This review chapter details a systematic approach to electrocardiogram (ECG) analysis. Accurate interpretation of ECGs requires thoroughness and care. Trainees should be encouraged to cultivate a comprehensive, disciplined method of reading ECGs that can be applied in every case. Many of the most common mistakes are errors of omission, specifically the failure to note subtle but critical findings. For example, overlooking a…

This chapter provides a brief introduction to an important aspect of everyday electrocardiogram (ECG) analysis related to the two major types of cardiac implantable electronic devices (CIEDs): pacemakers and implantable cardioverter–defibrillators (ICDs). The topic of implantable loop recorders (ILRs) is briefly described in 4, 13 . Additional material on CIEDs is provided in the online supplement and Bibliography. Pacemakers: Definitions and Types Key Point Pacemakers are…

Cardiac arrest occurs when the heart stops contracting effectively and ceases to pump blood. Sudden cardiac arrest is not a single disease per se but a complex syndrome having several electrocardiogram (ECG) manifestations and multiple causes. Furthermore, sudden cardiac arrest is not synonymous with acute myocardial infarction (MI; “heart attack”). However, MI—acute, recent, or previous—constitutes an important cause of sudden cardiac arrest. The closely related term…

Digitalis preparations (most commonly in the present era prescribed as digoxin) have been used in the treatment of heart failure and of certain supraventricular arrhythmias for over 200 years since their first description in the English scientific literature. However, digoxin can be a major cause of arrhythmias and conduction disturbances. Digoxin (digitalis) excess (which may lead to frank toxicity) continues to cause or contribute to major complications…

Preceding chapters have described the major arrhythmias and atrioventricular (AV) conduction disturbances. These abnormalities can be classified in multiple ways. This review/overview chapter categorizes arrhythmias into two major clinical groups: bradycardias and tachycardias. The tachycardia group is further subdivided into narrow and wide (broad) QRS complex variants. This differential diagnosis is a major focus of electrocardiogram (ECG) differential diagnosis in acute care medicine and in referrals…

The previous chapter focused primarily on disorders associated with delays in atrioventricular (AV) conduction, termed AV heart blocks. This chapter describes an entirely different class of AV conduction disorders, namely those related to abnormally early ventricular excitation ( preexcitation ). Our specific focus will be their most common presentations, namely Wolff–Parkinson–White (WPW) patterns and associated arrhythmia/conduction syndromes. This chapter also serves as an extension of the…

Normally, the only means of electrical communication (signaling) between the atria and ventricles is via the specialized conduction system of the heart. This relay network comprises the atrioventricular (AV) node, the bundle of His, and the bundle branch system ( Fig. 17.1 ). The atria and ventricles are otherwise electrically isolated from each other by connective tissue in the indented rings (grooves) between the upper and lower…

The three preceding chapters have focused primarily on supra ventricular arrhythmias, especially those related to rapidly occurring electrical disturbances arising in the area of the sinus node, the atria, or the atrioventricular (AV) node (junction). Assuming normal ventricular conduction, these rapid rhythms all produce narrow (normal QRS duration) complex tachycardias (NCTs). This chapter considers another essential electrocardiogram (ECG) topic: ventricular arrhythmias—the major but not the only…

This chapter discusses two of the most common and clinically important tachycardias: atrial flutter and atrial fibrillation (AF), schematized in Fig. 15.1 . Up to this point, we have focused primarily on those supraventricular tachycardias (SVTs) characterized by (1) organized atrial activity manifested by discrete P waves (when not hidden in the QRS), usually associated with (2) 1:1 atrioventricular (AV) conduction. a a The term 1:1 AV…

General Principles This chapter and the next two focus on rhythm disturbances with a rapid rate, namely supraventricular ( Fig. 14.1 ) and ventricular tachyarrhythmias. Key Concepts For any rapid, abnormal heart rhythm to occur, two major factors have to be present: A trigger that initiates the arrhythmia. A substrate that allows the arrhythmia mechanism to continue (self-sustain). Tachyarrhythmias, both supraventricular (see Fig. 14.1 ) and ventricular (see…

Part II of this book deals with physiologic and abnormal cardiac rhythms. Systematically analyzing the cardiac rhythm from the electrocardiogram (ECG) allows you to address two key and interrelated sets of questions: 1. What pacemaker is controlling the heartbeat? There are three major possibilities: a. The sole pacemaker is the sinus (sinoatrial [SA]) node. b. Sinus beats are present but interrupted by extra (ectopic) heartbeats. Ectopic…

A wide variety of major disease processes may alter the electrocardiogram (ECG). Particularly important are conditions affecting the pericardium (acute pericarditis, pericardial effusion, and constrictive pericarditis), the myocardium itself (not including ischemia and infarction, which are discussed separately in 9, 10 ), and the pulmonary system, including pulmonary embolism (acute and chronic thromboembolic disease), chronic obstructive pulmonary disease, and pulmonary parenchymal disease. Acute Pericarditis, Pericardial Effusion,…

A number of common factors, including drug effects, electrolyte abnormalities, and a variety of metabolic conditions affect the electrocardiogram (ECG). Indeed, this almost universally available and inexpensive bedside test may be the major, initial indicator of a life-threatening abnormality, such as hyperkalemia, hypocalcemia, and drug toxicities. We discuss these topics in this chapter, along with a brief review of nonspecific versus more specific ST-T changes. Key…

Myocardial infarction (MI) may be associated with the appearance of classic ST segment elevation MI (STEMI), usually followed by T wave inversions, as described in Chapter 9 . Q waves may appear in one or more of these leads. However, in many cases, myocardial ischemia (with or without actual infarction) presents with ST segment depressions rather than primary ST elevations. Q waves are less likely to develop…